〔Abstract〕 Objective To investigate the effect of RO or combined cholesterol(CH) on keratinocytes cell proliferation and cyclin expression. Methods The KCs were cultured with different concentrations of RO for different times,the proliferation of KCs were analyzed by MTS.Cell cycle of KCs were detected by flow cytometry after using RO with different times or combined treated with CH,and Western blot was used to reveal the expression of CyclinB1 and CyclinE. Results The RO inhibited the proliferation of KCs in a quantitative and time-dependent manner.Combined use of CH reduced the proliferation inhibition of RO on KCs.RO could significantly increase the proportion of KCs cell cycle in G1 phase,while combined use of CH reduced G1 phase growth rate of KCs cell cycle.Western blot demonstrated that use of RO could reduced the CyclinB1 and CyclinE content in the KCs in a time dependence manner.Combined use of CH antagonism RO down-regulated Cyclin E,but had no significant effect on the expression of CyclinB1. Conclusion RO inhibits the proliferation of KCs by down-regulating the expression of CyclinB1 and CyclinE which blocks the G1 phase of KCs cell cycle.